Packaging machine



Sept. 8, 1953 F. B. CASEY ET AL PACKAGING MACHINE Original Filed Nov. 26, 1947 m Wad m ww mw Q m ma .5 mam FRM%. w

Alfomey Patented Sept. 8, 1953 PACKAGING MACHINE Francis B. Casey,

Concord, Robert Reed Woodcock, Weymouth, and Manson E. Wood, Wakefield, Mass., assignors to Dewey and Almy Chemical Company, Cambridge, Mass., a corporation of Massachusetts Original application November 26,

1947, Serial No.

Divided and this application Decemher 6, 1949, Serial No. 131,418

1 Claim. (Cl. 154-42) This application is a division of patent application Ser. No. 788,262, filed November 26, 1947. In the parent application a machine was disclosed capable of removing air from filled bags formed of heat-scalable sheet or tube material and then sealing the bag in an hermetic manner by heat and pressure.

Claims in the parent application are directed to the machine itself. The present application is directed to the heat-sealing means which are used on the machine as described in the parent application, but which also are capable of use on other forms of sealing apparatus where a dependable heat-sealed hermetic closure is desired.

In sealing the open mouth of bags made of thin films of a heat-scalable substance, one serious difficulty has been improper sealing if the film happened to be creased or folded as the mouth of the bag was laid across the sealing jaws. If the bag is composed of a truly thermoplastic substance, the concentration of pressure on the ridge causes the material to flow excessively at the moment of sealing. The result is a spotty seal which frequently leaks, but more fre uently is mechanically weak.

This spotty, localized thinning of the bag substance adjacent the fused seal may be prevented by'making the support or anvil member flexible and distortable as, for example, making the anvil out of rubber, but immediately new troubles occur, chief of which is an overall weakening of the seal.

The specific object of this invention is to devise means for sealing a heat-scalable bag in an hermetic manner whether or not a fold or other irregularity of the thickness of the material in the area to be sealed is present and to devise means which prevent the heat-sealing jaws from weakening or tearing the bag as the jaws close.

Essentially, the machine described in the parent application consists of a suitable support for the bag and its contents, an evacuating nozzle over which the mouth of the bag is pushed during evacuation and a pair of sealing .1 aws arranged to engage opposite sides of the neck of the bag in front of the evacuating nozzle to heat seal the bag.

In our investigation of the cause of weak seals made with conventional sealing apparatus, we discovered that although one would expect that the heat derived from a single, hot sealing jaw would strike through the thin material of the bag so quickly that there would be no significant difierence in the physical condition of the film in the top and bottom layers of the bag at the moment of sealing, the cold opposing jaw chilled the layer in contact with it. The result is that one wall of the bag is plastic and flowable while the other wall is still relatively rigid. This effect concentrates the plastic flow during sealing to the hotter wall of the bag and produces a one-sided, weakened seal. We discovered also that if one-sided seals were to be avoided, the development of plasticity in both walls of the bag in the area to be sealed should progress approximately at the same rate. We accomplish the desired result and produce well sealed bags by heating both sealing jaws and by providing that at least one of the sealing bars be-hot and flexible and distortable when sealing is performed. In practice, the surface temperatures of the upper and lower bars are kept approximately equal.

:Figure 1 is a sectional detail through the two actual sealing members.

Figure 2 is a section jaws.

Figure 3 is a diagrammatic elevation of the sealing machine.

Referring to the drawings, the machine is prothrough both sealing vided with a supporting frame constructed generally as a rectangular box-like frame 10 having a table surface ll formed at the top thereof. Preferably, the frame It is formed of angle irons arranged along the various corners of the boxlike frame and secured together in any suitable manner. Adjustable foot pieces I2 are arranged at the four lower corners of the frame It and maintain the frame in spaced relation with respect to the floor or supporting surface.

A lower sealing jaw I3 is supported on the table surface I l, and a movable sealing ,iaw, represented generally at It, is arranged above the stationary jaw l3 and is mounted for vertical reciprocation on a movable frame having two vertical sides formed of two tubular members [5 and I6 having threaded engagement at their lower ends with vertical rods I! and I8. A

' horizontal cross bar I 9 in the form of an inverted channel iron extends between the vertical rods l1 and I8.

Mounted immediately below the center of the cross bar i9 is an operating cylinder 2!, such as a pneumatic cylinder, having a piston connected to the center of the bar I!) by a connecting rod 22. The upper sealing jaw I4 is mounted across the upper ends of tubular members I 5 and I 6. By suitably energizing the cylinder 2|, the sliding frame carrying the movable sealing heated by suitable electric heaterunitsiarranges within the bore 26 and is -maintainedatz: a;pr.e.-- determined temperature by a thermostatic elea ment mounted within the boreil. Astrip .or bar 28 of heat insulating material;,such.as.,asbestQS;. is interposed between the heated bar 24and;th,e; channel bar 25 to prevent loss of heat.

Electric current for heating jaw M isasupplied. by a cable 29 which passes upwardly through tubular; member ldta-a-connector-fil carried by ehannel bar 25; The. lbweitsealingjawisiorrned oif'a metallic bar SZI heated"; by suitable,-- electric units positioned.- in core 33:" and controlled: by; a thermostatic element positioned in here 3.4. A heat: insulating: strip 35" is" interposed between the-bar'- 32 and the: table II- to prevent-lossaof heat through the table;

The actual sealing surface of thelowerjaw is: formed from a strip ofheat-resistant; yield: able or'springymaterial 36;.such as silicone rubber'reinforced with glass fiber, arranged on the upper edge of" the bar 32 and held' in position by a pair'of clamping angle pieces 31 secured on opposite sides-oi the bar32'; The yieldable seal-'- ingstrip provides-a cushioning eifect to" seal across any'creases-or fOldSWVhiChi are found'in the neck of the bag. The springinessof the strip makes it possible to seal the thin sections between folds without using excessive pressure which would cut through the folded" portions. The silicone rubber strip is also useful in the sealing of thermoplastics which become sticky at sealing temperatures, since it' prevents sticking of the material to the jaw, andthe fact that it is heated approximately to the same tempera-- ture as jaw It prevents a one-sided weakening of the seal;

We also found when the bag was filled with material anditsneck was laid'on the lower sealing jaw l3; thepresence of material'in the has caused the walls of the bag to come together from spaced points so that at the moment of sealing, the bag walls approached" each other as a rather open v. At the same time, the down:- ward travel of the upper sealing jaw' Illstretched the plastic bag material in contact with the upper bar and thinned it thus weakening the seal. W e found that by rounding the inner edge of the upper bar 23 to form a radius 38, asharp heated line is not formed as the jaw 14 descends upon the, thermoplastic material and much less strain is imposed and a seal can be formed without producing a strip of thinned and weakened thermoplastic material on the contents side of the seal immediately adjacent the heatseal. As shown in Figure 1, the inner front edge of sealing bar 23 is rounded to prevent such a squeezing out and thinning down of'the bag material under the heat-sealing pressure. The sharp right-angle corner on the outer side of the bar allows the bag surplus to be torn off cleanly when the material is hot and plastic from the sealing; operation. Guard plates are.- arranged on..opposite,: si des,of thelower sealingzjaw to prevent burning of the hands of the operator by the jaw.

The operation of the machine will be summarized" as follows: When the bag has been filledwith. themater-ial to be packaged the neck oi.- the-bagdszplaced between the resilient heated lowenjaw: LSiandthe heated upper jaw Hi. The operator. then. actuates a control which moves the-upper jaw intosealing position with the neck of..the.bag.r Substantially a uniform pressure is built. up on the interposed thermoplastic materialof thee bag.- and no over pressures occur which cause the heated thermoplastic material tothin, flow and weaken the sealed portion of the bag.

The SeaISTWh'iChi are. formeck by: this apparatus are quite uniform, and: will stand. approximately the same strain as will the walls-zoithetbagz.

In. a; machine: for: heat: sealing: filled: bags: of thermoplastic; material,. the;- ccmbination" of. a heated flexible support niember providing a resilient: yieldable. anvil surface andqa movable heated. sealing jaw formed: of goodv heat con ducting property and adapted: to close: upon said anvilisurface and to heat seal thermoplastic material interposedbetween said: sealing; jaw and said anvil surface, means for heating. both jaws, the-sealing surface of said'ssealing jawand 01" said support member being fiat and mutually parallel in. the sealing position, one margin. of said sealing' jaw merging into the vertical face-oi said jaw as a radius facingthebag, said; radius being ofsufii'cient dimensions that no portion-of the bag contacts a;- substantially discontinuous surface of saidsealing jawas the jaw closes to form a seal whereby the heat. imparted bythe sealing-jaw to the thermoplastic bag materialis graduated from the bag to: the sealed area. and an area oi thihned and weakened thermoplastic material on the bag sideof the seal immediately adjacent the sealed area is avoided, and'theother margin of said-sealing jaw lying along a rectangular intersection of the sealing face with the other vertical face-of said sealing jaw;

FRANCIS B. CASEY. ROBERT REED WO-ODCOGK. MANSON E2 WOOD.

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1,953,122. Munson Apr. 3,1934 2-,2-13,744=- Robertson Sept. 3, 1940 2,258,218 Rochow- -.O.c.t. 7,1941 2,289,618- Youngv July 15:, 19.42 2,340,510.- Corely et a1. .Eeb.,1, 19.45 2.39.0,550- Moore. s Dec. .11, 19.45 2,433.176 VanEpps H,...Dec..23,.19A? 234513.552 Staw June, 21,.19A9 2,479,375 Langer Aug. 16, 19.4.9 2,434 976.. Collins.- ,Oct.. 11, 1949 2,509,339.. Langer .May 30, 19.5.0 

